The invention relates to an organic layer for subsequent coating with a cover layer which is harder than the organic layer. The invention also relates to a process for surface treatment of an organic layer which is intended to be subsequently coated with a cover layer which is harder than the organic layer.
Kuehnle et al., U.S. Pat. No. 5,211,995 discloses a process for coating organic surfaces with a cover layer which is harder than the organic layer. In this process the organic layer, in particular a clear finish lacquer of organic material on a metal sheet painted with colored lacquer is prepared for application of the cover layer by a cleaning operation. Subsequently, the prepared organic layer, which may, for example, be a clear final lacquer of a metal sheet or panel painted with colored lacquer, has the cover layer formed of material which is harder than the organic layer deposited thereon by means of the CVD (Chemical Vapor Deposition) process. For this purpose, the surface of the organic layer is cleaned, introduced into a reactor, the reactor is evacuated, a gas comprising a precursor material--referred to hereinafter as precursor material--is introduced, and the precursor material is energetically excited. When the process parameters are appropriately adjusted, the cover layer then deposits on the surface of the organic layer, i.e. on the clear lacquer. The material of the cover layer may be, in particular, silicon nitride (Si.sub.3 N.sub.4) and titanium nitride (TIN.sub.2). Cover layers of this type theoretically are particularly useful in the automobile field, since the cover layers exhibit substantial resistance against external, destructive influences, such as, for example, chemicals or mechanical stresses, i.e. scratches and the like. Furthermore, when a motor vehicle body is successfully coated, it is possible to omit supplemental waxing of the motor vehicle body, which is comparatively costly in financial terms and which also is associated with environmental costs during application and subsequent removal of the wax layer. It has proven to be problematic, however, that the quality of the overall layer construction consisting of an organic layer and a cover layer, is low. Thus, a layer construction of this type, for example, does not exhibit an optically uniform coloration, and the surface quality also is low. Furthermore, the resistance of the cover layer against chemical influences which further attack the organic layer and against possible mechanical influences, under which the cover layer, for example, fractures, remains far below the theoretically achievable protection of the organic layer.